In a single carrier based communication system operating at high carrier frequencies in either microwave (uWave) or E-band (eBand), phase noise from the transmit and receive radio frequency (RF) carrier local oscillators (LO) significantly corrupts transmission. Phase noise on the carrier is a significant impairment to supporting higher order modulations.
Digital baseband data is modulated, such as using 256-QAM (Quadrature Amplitude Modulation), onto a carrier and up-converted to an RF carrier frequency using an LO signal. Phase noise is introduced in the up-converted signal by the LO signal. This causes the QAM constellation to rotate as the LO phase changes over time.